A radiation image capturing apparatus (flat panel detector, also called a semiconductor image sensor) is developed. In such radiation image capturing apparatus, a plurality of radiation detecting elements are arranged two-dimensionally (matrix shape), charge is generated in the plurality of radiation detecting elements according to the amount of radiation which passes to the subject and is irradiated on the element, and a readout IC reads the charge as a signal value. A portable radiation image capturing apparatus (also called a FPD cassette) is developed. In such portable radiation image capturing apparatus, a sensor panel in which a plurality of radiation detecting elements are arranged is stored in a case.
Then, when radiation is irradiated a plurality of times on the conventional film/screen and stimulable phosphor plate, the problem of double exposure and multiple exposure occurs. However, the radiation image capturing apparatus reads out the signal value each time capturing is performed, and the signal value can be stored in the memory of the apparatus or transferred outside. Therefore, by using the radiation image capturing apparatus, the radiation can be irradiated a plurality of times on the capturing site of the subject, and moving image capturing such as dynamic capturing can be performed.
For example, when radiation is irradiated a plurality of times on a chest portion of a subject as the capturing site and dynamic capturing is performed, for example, as shown in FIG. 7, radiation images (that is, each frame image composing the dynamic capturing) showing the time phases T (T=t0−t6) of a lung field R of the patient can be obtained. By analyzing the frame images, it is possible to obtain a maximum inspiratory level, a maximum expiratory level, an expiratory term, and an inspiratory term of the lung field R. Attempts are made to further analyze the dynamic image to be applied to diagnosis.
When the readout process of the signal value is performed in the radiation image capturing apparatus, electronic component such as the above-described readout IC and the power source circuit may generate heat. For example, when the readout IC generates heat, the signal value read out as described above with the readout IC may change due to the heat, and the radiation image may not be suitably captured. The captured radiation image may be blurred due to the heat of the readout IC and the power supply circuit and this may worsen the quality of the image.
Therefore, for example, Patent Document 1 discloses a radiation image capturing apparatus in which one end of a heat releasing member formed from a metallic material with a high thermal conductivity such as aluminum and copper is connected to an electronic component in the radiation image capturing apparatus, and the other end of the heat releasing member is attached to the inner side of a case. The heat from the electronic component is released to the case through the heat releasing member. With this, the temperature of the electronic component rising can be prevented.